Compact Oldham coupling

ABSTRACT

A pair of keys of an Oldham coupling are located on a chord spaced from a diameter and are of a parallelogram shape. The ends of the corresponding slots are located at the same radius whereby a reduced envelope results.

BACKGROUND OF THE INVENTION

In scroll machines such as compressors there are two scroll memberswhich must be held to relative orbiting motion. Commonly, one of thescroll members is called a fixed scroll and the other scroll member iscalled an orbiting scroll. An Oldham coupling can be employed to holdthe fixed and orbiting scrolls to a relative orbiting motion. To achievethis, the Oldham coupling reciprocates with respect to the crankcasewhile the orbiting scroll reciprocates with respect to the Oldhamcoupling. The coactions are those of slots and keys and the Oldhamcoupling surrounds the hub of the orbiting scroll and possibly the axialcompliance or support structure. Movement of the Oldham coupling usuallytakes place within diameters. When considering the need to keep the keysin their slots for their full strokes and the need to avoid interferingwith the axial compliance or support structure, there can be asignificant increase in the envelope required to contain the Oldhamcoupling and the housing in which it is located. Alternatively, therecan be a significant reduction in the envelope available for the axialcompliance or support structure.

European Patent Application 0 479 412 A1 discloses an Oldham coupling ofan oval shape with one pair of keys located on a chord of a circularsection of the oval but located on "outwardly projecting flangeportions". These projecting flange portions extend beyond the diameterof the circular section. This achieves some reduction in the requiredenvelope by positioning the keys in regions where more operating spacemay be available.

SUMMARY OF THE INVENTION

One, or both, of the keys of a scroll compressor can be located onchords. The keys are configured to the shape of the corresponding ringportion of the coupling, namely a parallelogram. A diametral locationyields a special case of a parallelogram, the rectangle, and the sidesare coextensive as are those of the slot. As you move from a diametertowards a tangent, the sides in the direction of movement become lesscoextensive but the length of the slots increase. The present inventionconfigures the slots to the keys.

It is an object of this invention to reduce the radial clearance neededfor anti-rotation mechanisms.

It is a further object of this invention to maximize the size of theinternal structure while keeping the external structure constant.

It is an additional object of this invention to reduce the overall sizeof the surrounding structure while maintaining the size of the structureinternal to the Oldham coupling. These objects, and others as willbecome apparent hereinafter, are accomplished by the present invention.

Basically, at least one set of keys of an Oldham coupling are located ona chord and are shaped generally like the underlying portions of thering.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the present invention, reference shouldnow be made to the following detailed description thereof taken inconjunction with the accompanying drawings wherein:

FIG. 1 is a top view of the Oldham coupling of the present invention;

FIG. 2 is a bottom view of an orbiting scroll of the present invention;

FIG. 3 is a bottom view of the Oldham coupling of FIG. 1 engaging theorbiting scroll of FIG. 2;

FIGS. 4A-4D represent a PRIOR ART key and slot coaction at 90°intervals;

FIGS. 5A-5D represent the coaction of a key and slot of the presentinvention at 90° intervals;

FIG. 6 is a composite of the motion of FIGS. 4A-4D of the PRIOR ARTdevice showing all of the parts on center; and

FIG. 7 is a composite of the motion of FIGS. 5A-5D of the presentinvention showing the reduced envelope required.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In FIGS. 1-3, 5A-5D and 7, the numeral 10 generally designates an Oldhamcoupling made according to the teachings of the present invention.Oldham coupling 10 has a first pair of keys 10-1 and 10-2 which arelocated on a chord significantly displaced from a diameter. As is bestshown in FIG. 3, a second pair of keys 10-3 and 10-4 is located on aline, specifically, as illustrated, a diameter. The line on which keys10-3 and 10-4 are located is perpendicular to the cord on which keys10-1 and 10-2 are located, but on opposite sides of the Oldham coupling10.

In FIGS. 2, 3, 5A-5D and 7, the numeral 20 generally designates anorbiting scroll of a scroll compressor. Orbiting scroll 20 has a pair ofslots 20-1 and 20-2 which respectively receive and coact with keys 10-1and 10-2. As would be conventional, keys 10-3 and 10-4 would coact withcorresponding slots in crankcase 40 such that coupling 10 would be heldto a reciprocating motion. Similarly, the coaction of keys 10-1 and 10-2with slots 20-1 and 20-2 would hold orbiting scroll 20 to areciprocating motion with respect to the coupling 10 which is moving ata right angle thereto. As a result the orbiting scroll 20 is held to anorbiting motion with respect to the member, crankcase 40, that keys 10-3and 10-4 coact with.

In FIGS. 4A-4D and 6 the numeral 110 generally designates a PRIOR ARTOldham coupling with a conventional rectangular key 110-1 located on achord. An orbiting scroll 120 has a slot 120-1 coacting with key 110-1.The letter A designates the axis of the crankshaft of the scrollcompressor 200. The letter B designates the axis of the eccentricdriving the orbiting scroll 120 as well as the axis of scroll 120. FIG.6 illustrates the parts on center, with A and B coaxial whereas FIGS.4A-4D illustrate the relationship of the parts with B orbiting A at 90°intervals around orbit path C. Circle segment D represents the maximumclearance for solid internal components and/or clearances around thethrust bearing, etc. Building in from the inner radius of shell 130 ofcompressor 200 in FIG. 6, the key location is determined, asillustrated, through the upper left corner of slot 120-1 which runsclosest to the shell 130, a position about midway between that of FIGS.4B and 4C. It will be noted that coupling 110 is only capable ofreciprocating movement in a vertical direction, as illustrated, withrespect to crankcase 140 which underlies coupling 110 and has slots (notillustrated) which coact with keys (not illustrated) on coupling 110 ina conventional manner. The largest radius, corresponding to curve D, ofthe internal structure is determined by the key corner at the lowerright, a position corresponding to that of FIG. 4D.

Referring specifically to FIG. 6, the parts are on center so that axes Aand B are coaxial. E is the upper, outer point of key slot 120-1 and Fis the circle defining the orbit path of point E as orbiting scroll 120orbits. It should be noted that circles C and F are identical except fortheir locations. The curve G represents the minimum enclosing space andis only separated from the interior of shell 130 by design clearances.If point H rather than point E was the determining point for the minimumenclosing space, then circle F' which is the same as F and C, butdisplaced, would determine the location of the new, reduced enclosingspace defined by curve G'.

In FIGS. 5A-5D and 7, the letter A designates the axis of the crankshaftof scroll compressor 100 having a shell 30. The letter B designates theaxis of the eccentric driving the orbiting scroll 20 as well as the axisof scroll 20. FIG. 7 illustrates the parts on center, with A and Bcoaxial whereas FIGS. 5A-5D illustrate the relationship of the partswith B orbiting A at 90° intervals around orbit path C. Circle Drepresents the maximum clearance for solid internal components. Points Aand B, path C and circle D are the same values in FIGS. 4A-4D, 5A-5D, 6and 7.

Referring specifically to FIG. 7, the parts are on center so that axes Aand B are coaxial. Points L and M, which correspond to points E and H,respectively, of FIG. 6, are independently laid out with respect to theouter operating envelope or minimum enclosing space which is representedby curve G' in FIG. 6. As a result, circles N and O which respectivelydefine the orbit paths of points L and M are tangent to the same curve,P, which represents the outer operating envelope or minimum enclosingspace and corresponds to curve G' of FIG. 6 and represents a spacesaving defined by the difference of G and G' in FIG. 6 and roughly bythe difference of P and superimposed G in FIG. 7. .Iadd.Because allpoints of orbiting members orbit within the same size circular path,circles N and O are of the same size and, since circles N and O aretangent to the same circular curve P which represents the outeroperating envelope, then L and M, the centers of circles N and O, areequally spaced from circular curve P. Further, since P is a spacedclearance from the interior of shell 30, then L and M are also equallyspaced from shell 30. Referring to FIG. 5A it is readily seen that theouter surface of key 10-1 is effectively defined by a line throughpoints L and M with the two corner points of key 10-1 falling on curve Pin their extreme outermost position of orbit defined by circles N and O,respectively, as illustrated in FIG. 7. .Iaddend.In choosing points Land M the result is a parallelogram-shaped key 10-1 since L and M, asbest shown in FIG. 5A, represent the extremes of movement of key 10-1within slot 20-1. Key 10-1 has the same contact area with the sides ofslot 20-1 as key 110-1 has with slot 120-1.

While the present invention has been specifically described in terms ofa single slot and key coaction it is clear that the operation of theother key and slot of the pair would function in a mirror operation.

Although a preferred embodiment of the present invention has beenillustrated and described, other changes will occur to those skilled inthe art. For example, rather than decreasing the size of the shellrequired, the present invention can provide an increased clearance inthe same shell. Also, the keys 10-3 and 10-4 can coact with a member. Itis therefore intended that the scope of the present invention is to belimited only by the scope of the appended claims.

What is claimed is:
 1. A scroll machine having a shell with an axiscontaining a reference member, a coupling member and a scroll memberwith said coupling member coacting with said reference member and saidscroll member such that said scroll member is held to an orbiting motionwith respect to said reference member wherein:said coupling member isgenerally ring-shaped and has a center and a first pair of keys on afirst side with said first pair of keys being located on a chord spacedfrom said center and said axis; said first pair of keys being of aparallelogram shape with one pair of opposing sides of saidparallelogram being parallel to said chord; said scroll member having apair of slots parallel to said chord for receiving said first pair ofkeys and coacting therewith; each slot of said pair of slots extendingto an outer edge of said scroll member with each portion of said edgecorresponding to said slot being essentially equally spaced from saidaxis when said corresponding edge is closest to said shell; an outermostone of each second pair of opposing sides of said parallelogram beingessentially continuous with said portion of said edge corresponding to acorresponding slot when said corresponding edge is closest to said shellwhereby a reduced envelope is obtained.
 2. The scroll machine of claim 1wherein said coupling member has a second pair of keys coacting withsaid reference member. .Iadd.3. A scroll machine having a shell with anaxis containing a reference member, a coupling member and a scrollmember with said coupling member coacting with said reference member andsaid scroll member such that said scroll member is held to an orbitingmotion with respect to said reference member wherein:said couplingmember is generally ring-shaped and has a center and a first pair ofkeys on a first side with said first pair of keys being located on achord spaced from said center and said axis; said first pair of keyseach having a pair of opposing sides which are parallel to said chordand of generally equal length; said scroll member having a pair of slotsparallel to said chord for receiving said first pair of keys andcoacting therewith; each slot of said pair of slots extending to anouter edge of said scroll member with each portion of said edgecorresponding to said slot being essentially equally spaced from saidaxis when said corresponding edge is closest to said shell; an outermostone of a second pair of sides of each of said first pair of keys beingessentially continuous with said portion of said edge corresponding to acorresponding slot when said corresponding edge is closest to said shellwhereby a reduced envelope is obtained. .Iaddend..Iadd.4. The scrollmachine of claim 3 wherein said coupling member has a second pair ofkeys coacting with said reference member. .Iaddend.